1. Field of the Invention
The invention relates generally to design of handicap accessible buildings and more particularly to the design of buildings permitting handicap barrier-free access to multiple building levels without the use of mechanical lifting devices.
2. Background Art
Barrier-free access to building environments especially to living environments is an absolute essential for persons having limited mobility. The degree of limited mobility depends, of course, on the nature of an individual's handicap. However, the single most commonly faced problem by handicapped individuals is the requirement to negotiate stairs which interconnect the living environments in their residence. For some the barrier of the stairs is a minor impediment, but for others stairs present a significant, if not overwhelmingly impossible, barrier to overcome. Significantly, the construction cost, both for new construction and for retrofit construction, for providing barrier-free access is very expensive well exceeding the standard costs for non barrier-free construction.
Before the instant invention, the design of barrier-free handicap accessible living environments was accomplished in one of three principle ways: (1) Single level design; (2) mechanical lifting devices; or (3) ramps connecting full-height living levels. In the case of single level design, the entire building environment must be built on one level (“ranch” style design). This design option requires a building foot-print that is of a size equal to the total building environment. In comparison to multi-level designs, the ranch design uses the most land, and therefore will not fit on many building lots where multi-level designs will fit. A ranch design, in comparison to a multi-level design, requires the greatest amount of excavation, foundation, exterior walls, concrete floor slab and roof in proportion to the total livable space. As a consequence of this inherent inefficiency, ranch designs cost more than multi-level building designs to build for the same area of livable space. The ranch design eliminates the need for mechanical lifting devices because there are no multiple levels but at a higher construction cost and restriction on the building lot size availability.
Mechanical devices can be used to provide access between multiple levels. For example multiple building levels can be interconnected and thereby accessed by means of mechanical devices that lift an individual or a wheel-chair from one level to another. A lifting device such as an elevator, wheel-chair lift, stair-climbing chair, moving stairway, etc. can be incorporated into the design. Mechanical devices such as these permit the designer to enjoy the cost and land saving benefits that derive from multi-level building design. However, all mechanical designs require significant initial costs for: (1) structural improvements required to accommodate the devices; (2) the devices themselves; and (3) installation of the devices. Additionally, mechanical designs are subject to on-going expenses, risks and inherent design limitations related to inspection, maintenance, repair, replacement, and limited lifting capacity and the limited area that moves between the multiple building levels.
For example, at the time of initial construction, a person may require a small elevator suitable only for one person to stand. Subsequently, increased disability may require the use of a wheelchair that requires a larger sized and increased weight-lifting capacity elevator. Also mechanical devices require electricity and have wearing parts and can, therefore, become inoperative because of power failure or mechanical breakdown. Handicapped individuals may become stranded or trapped in life-threatening circumstances in the event of power failure or mechanical breakdown.
Ramps are the third design option that permits barrier-free access to building environments. Ramps are sometimes used to interconnect multiple building levels for both commercial and residential uses. However, to be accessible for both able and disabled individuals, ramps can not exceed certain design limitations regarding their slope. For example, there are physical limits on how steep a slope can be for comfortable use by an able-bodied individual as well as partially disabled individuals. There are also physical limits on how steep a slope can be, in combination with the spacing of intermediate landings, for practical and comfortable use by individuals who propel themselves by hand-power in a wheel chair. There are also safety limits on how steep a slope can be used by persons in either hand-powered or motorized wheel chairs. This safety issue arises because there is a risk that a wheel chair may topple forward or backward or sideways because such chairs have a relatively high and therefore inherently unstable center of gravity.
In this connection, the American Disabilities Act Accessibility Guidelines (“ADAAG”) as amended in 1998 contains specifications for publically accessible new construction that are widely accepted throughout the United States of America for ramp design. The ADAAG defines a ramp as “walking surface which has a slope in the direction of travel that is greater than 1:20” (5% grade) (reference ADAAG 3.5). ADAAG section 4.8.2. specifies ramp design as follows:                4.8.2* Slope and Rise. The least possible slope shall be used for any ramp. The maximum slope of a ramp in new construction shall be 1:12. The maximum rise for any run shall be 30 in (760 mm).Additionally, the ADAAG requires a level maneuvering space that is at least five feet long at the bottom and top of every ramp. These design parameters result in a significantly long ramp where the total rise from one living level to another is nine feet (or one hundred eight inches).        
Because the maximum rise per run may be no more than thirty inches, a one hundred eight inch rise requires four ramp segments, each connected to the other by a sixty inch level landing. The total run of ramps also requires an additional sixty-inch level maneuvering area at the top and bottom of the highest and lowest ramps in the run of ramps. Five landings are therefore required, for a total of three hundred inches of level run for all landings. Additionally, the four ramps comprise a total horizontal run of one thousand, two hundred, ninety-six inches (108″×12=1,296″). The total required run of ramps and landings is therefore one thousand, five hundred, ninety-six inches, or a total horizontal run of one hundred thirty-three feet.
Typically ramps designed to the full ADAAG standard become so long that it is impractical to fit them into most allowable housing footprints or residential building lots. In some cases, although the ramp may fit within the allowable footprint, the cost of the ramp in proportion to the other costs of the building's usable space becomes prohibitive. In residential construction, shorter length ramps with greater slope may be used depending on the nature and extent of the person's disability. What is required therefore is a way to incorporate relatively shallow ramps in residential construction at reasonable cost to provide access to multi-level dwellings.